St. Louis County and the city of St. Louis are suing to stop the enactment of a new state law that penalizes police officers for enforcing federal gun laws.

House Bill 85 circumvents federal gun regulations, carrying a fine of $50,000 for each police officer that attempts to enforce such rules. The bill’s vague language also indicates that any communications between local law enforcement and federal agents about a weapon could be a fineable offense.

The law has drawn criticism from gun control advocates and law enforcement alike. Police chief Philip Dupuis of O’Fallon resigned from his position over concerns about the law’s enforcement. The Missouri Sherriff’s Association has also come out against HB 85. And Democratic St. Louis mayor Tishaura Jones said in a press release that the bill will make Missouri a “sanctuary state for gun violence.” She noted that “2020 was the deadliest year of gun violence in our state’s history, and now the Missouri legislature is throwing up barriers to stop police from doing their most important job —preventing and solving violent crime.”

Missouri Governor Mike Parsons said at the bill’s signing that its purpose was to “stand up to the federal government” and to stop Democrats such as President Joe Biden and Kamala Harris from “coming to the front doors of Missourians and taking their guns.”

The lawsuit seeks an injunction to halt the implementation of this law and argues that it should be overturned because it violates the Supremacy Clause of the US Constitution. The Department of Justice sent a letter to Parsons and Missouri attorney general Eric Schmitt last week warning them that they could not simply ignore federal laws. They wrote back that they “would not stand by while the federal government tries to tell Missourians how to live their lives.”